In the preparation of semiconductor devices such as IC and LSI, it has heretofore been a common practice that various steps such as photolithographic step using a photoresist composition, etching step, impurity diffusion step and wiring step are repeated several times. In the foregoing photolithographic step, a photoresist composition is applied to a semiconductor substrate to form a thin film thereon. The thin film is irradiated with actinic rays through a mask pattern, and then developed to form a resist pattern. As the actinic rays there have been used g-line (436 nm), i-line (365 nm), etc. However, with the enhancement of integration of semiconductor devices, light rays having a shorter wavelength such as far ultraviolet rays and exima laser have been used more and more. The shorter the wavelength of the actinic light rays used, the more light is reflected from the substrate. This causes a great problem that the resist pattern is liable to local strain (notching) or deterioration of dimensional accuracy due to reflected light. Thus, the interposition of an antireflective coating film between the substrate and the resist layer for the purpose of inhibiting the reflection of light has been noted (see JP-B-3-67261 (The term "JP-B" as used herein means an "examined Japanese patent publication")).
With the reduction of the wavelength of the actinic light rays used, emphasis has been placed on resists having a high resolution more and more. These resists have been extensively studied. However, if a resist composition having a high resolution is applied to a substrate having an antireflective coating film formed thereon, a so-called intermixed layer can be easily formed at the interface of the resist composition layer with the antireflective coating film, causing the lower part of the resist pattern to be bitten or expanded and hence making it impossible to form a resist pattern having an excellent section shape. Thus, good semiconductor devices can be hardly produced. This disadvantage becomes remarkable particularly with a chemically-sensitized resist composition capable of forming a resist pattern having an excellent dimensional accuracy and resolution. In order to eliminate these difficulties, an approach involving heat treatment at temperatures higher than 180.degree. C. has been proposed. However, this approach is disadvantageous in that the dye in the antireflective coating film can be easily sublimated, causing stain in the apparatus and other troubles. Thus, this approach is of no practical use.